Deck 24: Speciation

Question 1

Which of the following does not tend to promote speciation?

A) polyploidy
B) gene flow
C) natural selection
D) the founder effect

Answer 1

B

Question 2

Use the following information when answering the corresponding questions).
About 3 million years ago, the Isthmus of Panama a narrow strip of land connecting North and South America) formed, divid marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sid isthmus. Based on the morphospecies concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated
by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629- 32.)
If the isthmus formed gradually rather than suddenly, what pattern of genetic divergence would you expect to find in these species pairs?

A) greater percentage of difference in DNA sequence between species that inhabit deep water than between species that inhabit shallow water
B) greater percentage of difference in DNA sequence between species that inhabit shallow water than between species that inhabit deep water
C) similar percentages of difference in DNA sequence between all pairs of sister species

Answer 2

A

Question 3

Two researchers experimentally formed tetraploid frogs by fertilizing diploid eggs from Rana porosa brevipoda with diploid sperm from Rana nigromaculata. When they mated these tetraploid frogs with each other, most of the offspring that survived to maturity were tetraploid, with chromosome sets of both diploid parent species. Based on these results, if this type of tetraploid formed in the wild, what would be the result? Y. Kondo and A. Kashiwagi. 2004. Experimentally induced autotetraploidy and allotetraploidy in two Japanese pond frogs. Journal of Herpetology 383):381- 92.)

A) The two parent species would interbreed and fuse into one species.
B) The tetraploids would be reproductively isolated from both parent species.
C) The tetraploids would be selected against.
D) The two parent species would recognize each other as mates.

Answer 3

B

Question 4

You want to study divergence of populations, and you need to maximize the rate of divergence in order to see results within the period of your grant funding. You will form a new population by taking some individuals from a source population and isolating them so the two populations cannot interbreed. What combination of characteristics would maximize your chance of seeing divergence in this study?
1) Choose a random sample of individuals to form the new population.
2) Choose individuals from one extreme to form the new population.
3) Choose a species to study that produces many offspring.
4) Choose a species to study that produces a few, large offspring.
5) Place the new population in the same type of environment as the source population.
6) Place the new population in a novel environment compared to that of the source population.

A) 1, 3, and 5
B) 1, 3, and 6
C) 2, 3, and 5
D) 2, 3, and 6
E) 2, 4, and 6

Question 5

What keeps the two populations separate?

A) lack of hybrid viability
B) behavioural reproductive isolation
C) gametic barrier
D) geographic reproductive isolation
E) temporal reproductive isolation

Question 6

How are two different species most likely to evolve from one ancestral species?

A) phylogenetically, due to heterozygote advantage in hybrids
B) allopatrically, after the ancestral species has split into two populations
C) sympatrically, by a point mutation affecting morphology or behavior

Question 7

Many songbirds breed in North America in the spring and summer and then migrate to Central and South America in the fall. They spend the winter in these warmer areas, where they feed and prepare for the spring migration north and another breeding season. Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species?

A) The two species do not breed in the same area, so they are reproductively isolated by allopatry.
B) One of the species is probably polyploid, so they are reproductively isolated by genetic incompatibility.
C) They must have strong prezygotic or postzygotic isolating mechanisms in order to spend winter in such close proximity.
D) Reinforcement must be occurring when they winter together.

Question 8

Three populations of crickets look very similar, but the males have courtship songs that sound different. What function would this difference in song likely serve if the populations came into contact?

A) both a prezygotic and a postzygotic isolating mechanism
B) intrasexual selection between a male of one population and males of the other two populations
C) intersexual selection between a male of one population and females of the other two populations
D) a prezygotic isolating mechanism
E) a postzygotic isolating mechanism

Question 9

In hybrid zones where reinforcement is occurring, you should see a decline in

A) speciation.
B) mutation rates.
C) gene flow between distinct gene pools.
D) hybrid sterility.
E) the genetic distinctness of two gene pools.

Question 10

Use the following information when answering the corresponding questions).
About 3 million years ago, the Isthmus of Panama a narrow strip of land connecting North and South America) formed, divid marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sid isthmus. Based on the morphospecies concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated
by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629- 32.)
The sister populations on opposite sides of the isthmus are true species under which species concept?

A) the morphospecies concept
B) the biological species concept
C) the phylogenetic species concept
D) both A and C
E) all of the above

Question 11

The peppered moth has a light and dark colour morph; the light morph was common in pre- industrial England. Increased pollution during the Industrial Revolution allowed dark morph moths to camouflage effectively against the dark, sooty background. Consequently, the dark morph became more common in industrial areas while the light morph remained common elsewhere. Recently, dark morph moths have been decreasing with reductions in pollution. Should the two morphs be considered separate species?

A) No, because they are not in allopatry.
B) Yes, because the dark and light morphs have higher fitness in different habitats.
C) Yes, because natural selection has acted on the frequency of the two forms.
D) Yes, because they have very different phenotypes.
E) No, because there is no evidence that they are reproductively isolated.

Question 12

House finches were found only in western North America until 1939, when a few individuals were released in New York City. These individuals established a breeding population and gradually expanded their range. The western population also expanded its range somewhat eastward, and the two populations have recently come in contact. If the two forms were unable to interbreed when their expanding ranges meet, what would this situation illustrate?

A) sympatric speciation
B) vicariance
C) allopolyploidy
D) autopolyploidy
E) allopatric speciation

Question 13

A population of earthworms lives on an island in the middle of a river. Damming of the river causes flooding on the island, and only the highest points remain above water, creating several smaller islands with
Now- separate earthworm populations on them. The earthworms cannot swim. Which of the following best describes this event?

A) The earthworms have undergone speciation by sympatry.
B) The earthworm populations will still have gene flow between them.
C) The earthworm populations have been isolated by vicariance.
D) The earthworms have undergone speciation by allopatry.
E) The earthworm populations have been isolated by dispersal.

Question 14

Which of the following statements explains why animals are less likely than plants to speciate by polyploidy?

A) Animals are more mobile, so populations get separated far less often.
B) Animals are better at recognizing appropriate mates.
C) Animals have better mechanisms for repairing chromosomes than plants have.
D) Animals self- fertilize less often than plants, so diploid gametes are less likely to fuse.

Question 15

The two populations are

A) different species, under the phylogenetic species concept.
B) different species, under the biological species concept.
C) different subspecies, under the morphospecies concept.
D) All of the above.

Question 16

Most causes of speciation are relatively slow, in that they may take many generations of organism to see changes, EXCEPT

A) colonization.
B) vicariance.
C) polyploidy.
D) natural selection.

Question 17

Why is speciation by polyploidy more likely in plants than in animals?

A) Plants lack the DNA repair enzymes that animals have.
B) Plants are sessile and cannot speciate via dispersal.
C) Plant gametes can be produced from somatic cells that have undergone many rounds of mitosis.
D) Plant gametes lack postzygotic isolating mechanisms.

Question 18

Use the following information when answering the corresponding questions).
About 3 million years ago, the Isthmus of Panama a narrow strip of land connecting North and South America) formed, divid marine organisms into Pacific and Caribbean populations. Researchers have examined species of snapping shrimp on both sid isthmus. Based on the morphospecies concept, there appeared to be seven pairs of species, with one species of each pair in the Pacific and the other in the Caribbean. The different species pairs live at somewhat different depths in the ocean. Using mitochondrial DNA sequences, the researchers estimated phylogenies and found that each of these species pairs, separated
by the isthmus, were indeed each other's closest relatives. The researchers investigated mating in the lab and found that many species pairs were not very interested in courting with each other, and any that did mate almost never produced fertile offspring. N. Knowlton, L. A. Weigt, L. A. Solorzano, D. K. Mills, and E. Bermingham. 1993. Divergence in proteins, mitochondrial DNA, and reproductive incompatibility across the Isthmus of Panama. Science 260:1629- 32.)
Which of the following describes the most likely order of events in speciation?

A) divergence, genetic isolation, genetic drift
B) genetic isolation, divergence, genetic drift
C) divergence, genetic drift, genetic isolation
D) genetic drift, genetic isolation, divergence
E) genetic isolation, genetic drift, divergence

Question 19

The snake family Typhlopidae consists of small, burrowing species with vestigial eyes. They are found in Australia, sub- Saharan Africa, India and some adjacent areas, and South America. What is the most likely explanation for this distribution?

A) convergent evolution in the different regions
B) rafting to the different continents from the point of origin on one of these continents
C) origin on Gondwana followed by continental drift and some range expansion
D) all of the above

Question 20

Which of the following could be a vicariance event for species in that habitat?

A) Nonnative rats are introduced to an island by human explorers.
B) Radiation near Chernobyl increases mutation rate, causing an increase in autopolypolidy.
C) Some insects get blown in a storm to a new mountain range, where they lay eggs.
D) The level of water in a lake recedes, creating two lakes where there used to be one.

Question 21

Which of the following is true regarding speciation by polyploidy?

A) Scientists have only identified two cases of allopolyploidy leading to speciation in nature.
B) Polyploidy results in decreased rates of speciation.
C) Polyploids have higher levels of heterozygosity than their diploid relatives.
D) Allopatric speciation is faster than sympatric speciation by polyploidy.
E) Speciation by polyploidy occurs at similar rates in animals and plants.

Question 22

A species of groundhog spreads through an environmentally varying region surrounding a lake; the different populations, each in their own environments, accumulate habitat- specific morphological traits. Which of the following is this an example of?

A) species cluster
B) sub- species
C) allopatric speciation
D) founder effect

Question 23

A storm brings two formerly separated populations of beetles together. They look very similar. Under the biological species concept, which of the following would show that the two populations are different species?

A) When individuals from the two populations mate with each other in the laboratory, the eggs fail to hatch.
B) One population breeds in spring, the other in fall.
C) Males of the two populations have different flight patterns in courtship.
D) All of the above are correct.
E) None of the above are correct.

Question 24

Six potential species of seaside sparrows were genetically analyzed to determine their phylogenetic relationships. DNA analysis revealed that there were only two monophyletic groups with individuals from three subspecies making up each group. The three Atlantic coast subspecies formed one monophyletic group, while the three Gulf coast subspecies made up the other monophyletic group. If you could only save two subspecies of the seaside sparrows from extinction, would you choose two subspecies from the Atlantic coast, two from the Gulf coast, or one each from the Atlantic and Gulf coasts?

A) Save two subspecies from the Atlantic coast, as this coastline is longer and more likely to provide habitat for the birds.
B) Save one each from the Atlantic and Gulf coasts to preserve more genetic diversity.
C) Save two subspecies from the Gulf coast, as this area is much warmer and birds are more likely to survive.

Question 25

Imagine two North American ground cricket species that contact each other as the southern species moves northward during a period of global warming. These two species do not mate much, due to differences in their courtship songs. The northern cricket does not seem to tolerate the warmer temperatures well, but is limited in its ability to move north because it does not normally disperse much. Based on this information, which is the most likely outcome?

A) extinction of one of the species
B) hybrid zone formation
C) fusion of the populations
D) reinforcement
E) creation of a new species

Question 26

Which of the following reproductive barriers would prevent a mating attempt?

A) behavioural isolation
B) gametic isolation
C) sexual selection
D) hybrid sterility
E) mechanical isolation

Question 27

Which of the following evolutionary processes is not acting when two groups of organisms are identified as different species according to the Biological Species Concept?

A) mutation
B) gene flow
C) sexual selection
D) natural selection
E) genetic drift

Question 28

Two species of tree frogs that live sympatrically in the northeastern United States differ in ploidy: Hyla chrysocelis is diploid, and Hyla versicolor is tetraploid. The frogs are identical in appearance, but their mating calls, which females use to find mates, differ. Which difference most likely evolved first?

A) polyploidy
B) difference in mating calls
C) A and B must have occurred at the same time.

Question 29

A population of ground squirrels is separated by a glacier. Changes in which of the following would most likely result in reproductive isolation if the two populations came into contact several generations later?

A) A change in the gene encoding of a receptor on the egg- cell surface in one group.
B) A change in the fur colour of one group.
C) A change in the diet of one group.
D) A change in the alarm call of one group to warn of predators.

Question 30

You are studying two populations of spiders of the Dolomedes genus, characterized by a light stripe down each side of the body. One population lives in a pond, while another nearby population lives in the trees. Which of the following species concept would you be using if you determined that these were two different species?

A) morphospecies
B) ecological
C) phylogenetic
D) biological

Question 31

The common edible frog of Europe is a hybrid between two species, Rana lessonae and Rana ridibunda. The hybrids were first described in 1758 and have a wide distribution, from France across central Europe to Russia. Both male and female hybrids exist, but when they mate among themselves, they are rarely successful in producing offspring. What can you infer from this information?

A) These two species are likely in the process of fusing back into one species.
B) The hybrids form a separate species under the biological species concept.
C) Postzygotic isolation exists between the two frog species.
D) Prezygotic isolation exists between the two frog species.

Question 32

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South America. If reinforcement of prezygotic isolation is occurring, what would you expect if you compare the calls of the two species in zones of sympatry versus zones of allopatry?

A) Calls would be about the same in both areas.
B) Calls would be more different in areas of sympatry.
C) Calls would be more similar in areas of sympatry.
D) There is not enough information to decide what is happening.

Question 33

You are studying lizards in the field. The range of the northern population, species 1, overlaps the range of the southern population, species 2. You find hybrids in the zone of overlap. What is happening?

A) The postzygotic isolating mechanisms aren't working.
B) Hybrids are best adapted to this region where overlap occurs.
C) Reinforcement is occurring.
D) There is not enough information to decide what is happening.

Question 34

Male frogs give calls that attract female frogs to approach and mate. Researchers examined mating calls of closely related tree frogs in South America. What outcomes can occur where the ranges of two species overlap?

A) A stable hybrid zone will form if hybrids are better adapted to the area of overlap than either parent species is.
B) Species will continue to diverge and be isolated by behavioral or genetic mechanisms.
C) The species will interbreed, eventually fusing over time.
D) All of the above are possible outcomes.
E) None of the above are a possible outcome.

Question 35

A small number of birds arrive on an island from a neighboring larger island. This small population begins to adapt to the new food plants available on the island, and their beaks begin to change. About twice a year, one or two more birds from the neighboring island arrive. What effect do these new arrivals have?

A) Their arrival tends to slow adaptation to the new food plants.
B) Their arrival represents a colonizing event.
C) Their arrival tends to promote adaptation to the new food plants.
D) Their arrival speeds the process of speciation.

Question 36

Natural selection for traits that keep distinct populations from reproducing with each other is called reinforcement. When is reinforcement beneficial?

A) when prezygotic isolating mechanisms are in place
B) when populations would otherwise fuse over time
C) when hybrids have lower fitness than either parent population
D) when one population could be overwhelmed by the other

Question 37

Which of the following reproductive barriers would prevent a hybrid zygote from developing into a viable, fertile adult?

A) hybrid sterility
B) gametic hybridization
C) behavioural isolation
D) mechanical isolation

Question 38

A researcher notices that in a certain moth species, some females prefer to feed and lay eggs on domesticated solanaceous plants like potatoes and tomatoes. Other females prefer to feed and lay eggs on wild solanaceous plants like Datura. Both male and female moths primarily use scent to find these plants from afar. Females tend to mate where they feed, and the researcher finds a genetic basis for scent preference in these moths. Based on the above information, what might be occurring in this moth species?

A) divergence due to vicariance
B) postzygotic isolation
C) divergence in sympatry
D) polyploidization

Question 39

Which of the following is a disadvantage of the morphological species concept?

A) Two groups may use very similar resources, but be evolutionarily independent.
B) It is subjective in nature, with differences of opinion that cannot be resolved by data.
C) Reliable information exists only for a small number of organisms.
D) It cannot be used to evaluate fossils.

Question 40

If a plant species with 2n = 14 forms an allopolyploid with a plant species with 2n = 18, what would be the likely diploid 2n) number of the allopolyploid?

A) 36
B) 28
C) 32
D) 16